Correction, you can buy the Lotro expansions with the coins after the expansion has been launched to players that paid to buy it, isengard was like a week and a half after people buy it, you cant pre-order with turbine points. Bioware could very well do the same after the expansion has launched like lotro does, they have not said eiether way so at the moment it is no different to lotro.
But the fact is you can still buy the game with your coins you earn with your sub , correct? ? Or am i wrong??
You won't be able to do that here , and yes it has been said that you cannot buy with cartel coins.